+ arm64-mm-fix-destructor-for-unconstructed-hotplug-page-tables.patch added to mm-unstable branch

+ arm64-mm-fix-destructor-for-unconstructed-hotplug-page-tables.patch added to mm-unstable branch

[Andrew Morton]

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain, Size: 4099 bytes --]


The patch titled
     Subject: arm64/mm: fix destructor for unconstructed hotplug page tables
has been added to the -mm mm-unstable branch.  Its filename is
     arm64-mm-fix-destructor-for-unconstructed-hotplug-page-tables.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/arm64-mm-fix-destructor-for-unconstructed-hotplug-page-tables.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Before you just go and hit "reply", please:
   a) Consider who else should be cc'ed
   b) Prefer to cc a suitable mailing list as well
   c) Ideally: find the original patch on the mailing list and do a
      reply-to-all to that, adding suitable additional cc's

*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

The -mm tree is included into linux-next via various
branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there most days

------------------------------------------------------
From: Muchun Song <muchun.song@linux.dev>
Subject: arm64/mm: fix destructor for unconstructed hotplug page tables
Date: Sat, 10 Oct 2026 19:24:57 +0800

Commit c594b83457cc ("arm64: mm: call pagetable dtor when freeing
hot-removed page tables") made free_hotplug_pgtable_page()
unconditionally run the page-table destructor. This matches page tables
allocated by the arm64 mapping code, which runs the corresponding
constructors.

However, arm64 also uses the generic sparse-vmemmap population code.
Runtime intermediate page tables allocated by that code do not run a
page-table constructor. Freeing one during memory hot-remove therefore
runs a destructor without a matching constructor and corrupts
NR_PAGETABLE accounting.

Free intermediate page-table pages through pagetable_free(). It runs the
destructor only for constructor-backed pages and then releases the page
through the page-table freeing path.

Link: https://lore.kernel.org/20261010112457.49485-5-songmuchun@bytedance.com
Fixes: c594b83457cc ("arm64: mm: call pagetable dtor when freeing hot-removed page tables")
Signed-off-by: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Assisted-by: LLM
Cc: David Hildenbrand <david@kernel.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Paul Walmsley <pjw@kernel.org>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Alexandre Ghiti <alex@ghiti.fr>
Cc: Björn Töpel <bjorn@rivosinc.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Kevin Brodsky <kevin.brodsky@arm.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: <stable@vger.kernel.org>
---

 arch/arm64/mm/mmu.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

--- a/arch/arm64/mm/mmu.c~arm64-mm-fix-destructor-for-unconstructed-hotplug-page-tables
+++ a/arch/arm64/mm/mmu.c
@@ -1495,8 +1495,7 @@ static void free_hotplug_page_range(stru
 
 static void free_hotplug_pgtable_page(struct page *page)
 {
-	pagetable_dtor(page_ptdesc(page));
-	free_hotplug_page_range(page, PAGE_SIZE, NULL);
+	pagetable_free(page_ptdesc(page));
 }
 
 static bool pgtable_range_aligned(unsigned long start, unsigned long end,
_

Patches currently in -mm which might be from muchun.song@linux.dev are

mm-sparse-vmemmap-drop-vmemmap_populate_dax.patch
mm-sparse-vmemmap-support-device-dax-in-common-vmemmap-path.patch
mm-sparse-vmemmap-drop-device-dax-specific-population-path.patch
mm-sparse-vmemmap-remove-the-unused-ptpfn-argument.patch
mm-sparse-vmemmap-open-code-vmemmap_populate_address.patch
mm-mm_init-add-zone-mismatch-warning-during-page-init.patch
mm-fix-missing-page-table-destructor-in-pagetable_free.patch
riscv-mm-fix-hotplug-page-table-destructor-handling.patch
riscv-mm-fix-missing-destructor-for-hotplug-pud-tables.patch
arm64-mm-fix-destructor-for-unconstructed-hotplug-page-tables.patch